Electronic fuel control systems are increasingly being used in internal combustion engines to precisely meter the amount of fuel required for varying engine requirements. Such systems vary the amount of fuel delivered for combustion in response to multiple system inputs, including throttle angle and the concentration of oxygen in the exhaust gas produced by combustion of air and fuel. Typical electronic fuel control systems operate in a closed-loop mode in response to sensed exhaust oxygen level in order to maintain the ratio of air and fuel at or near stoichiometry.
As described in the above-noted U.S. patent application Ser. No. 08/172,782, it has been found advantageous to augment the capabilities of the electronic fuel injection control system in vehicles powered with compressed natural gas to compensate for variations in fuel pressure, ambient temperature, compressed natural gas temperature, and injector temperature. As disclosed in that prior application, this compensation may be advantageously provided by altering the duration of the fuel injection command signals by a predetermined correction value selected from a previously determined set of such values stored in a lookup table device, the value selection being performed in joint response to both the current fuel pressure and current injector temperature. As further noted in that prior application, the correction value which is used to adjust the injector command signal duration is preferably determined in pan by the current magnitude of the electrical potential supplied to actuate the injectors.